1. Field of the Invention
The present invention relates to a technology for communication between two devices located in different networks.
2. Description of the Related Art
Recent years have seen the widespread use of a technology by which two devices located in different networks operate in cooperation with each other to provide users with service.
For example, a technology comes into widespread use in which a personal computer located in a corporate Local Area Network (LAN) and a web server located in an Application Service Provider (ASP) network cooperate with each other to deliver information such as news via the Internet.
In general, the LAN is provided with a firewall. Such a firewall is so set that access from an external device to a device in the LAN is restricted more tightly than access from a device in the LAN to an external device.
In order for a user to obtain information from a web server, he/she needs to have access to the web server from a personal computer of the LAN to establish a session. In usual settings for a firewall, access from a web server to a personal computer of the LAN is prohibited in many cases.
To cope with this, the following method has been proposed. A managed device, a managing device for managing the managed device, and a relay server are connected to the Internet. The managed device has access to the relay server to obtain from the server first transfer information to be transferred to the managed device, or, sends to the relay server second transfer information to be transferred to the managing device. The managing device has access to the relay server to obtain the second transfer information from the relay server, or, to send the first transfer information to the relay server (Japanese Laid-open Patent Publication No. 2002-082792). Stated differently, both the managed device and the managing device save information to be sent to the other end of communication to the relay server. Then, each of the managed device and the managing device has access to the relay server to download therefrom information that has been sent to the device itself.
The method described in Japanese Laid-open Patent Publication No. 2002-082792 enables communication between the managed device and the managing device independently of a firewall.
However, data sent and received between the managed device and the managing device always pass through the relay server. Therefore, increase in communication puts more loads onto the relay server.
The present invention has been achieved in light of such an issue, and an object thereof is to perform communication via a firewall with loads put onto a relay server reduced as compared with conventional methods.